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  • 1
    Electronic Resource
    Electronic Resource
    Gametogenesis in the green algaOedogonium cardiacum (1973)
    Springer
    Protoplasma 78 (1973), S. 21-39 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mitoses and cytokineses leading to the formation of male and female gametes inOedogonium cardiacum are described at the ultrastructural level. Preceeding spermatogenesis, the nucleus and spindle are apically polarized for the first division, abutting the end wall near a ring which is much smaller than that characteristic of vegetative division. Cell division then cuts off a small, discoidal antheridial cell, a process repeated several times for each vegetative cell. The antheridial cell then divides once or twice more, generally transversely and/or longitudinally, but wall rupture and ring expansion play no role in these latter divisions. Fusion of vesicles lead to cross wall formation during the first two divisions, but membrane furrowing through the phycoplast partitions the daughter spermatids at the third and last cytokinesis. Discrete but amorphous bodies inside the poles of spermatogenous spindles are interpreted as Microtubule-Organizing-Centers, responsible for organizing the spindle microtubules. The nucleus and spindle are also highly polarized for the division that forms an oogonium and its complementary suffultory cell. However, polarization is now strongly basal, and the asymmetric cytokinesis partitions the cell so that most of the cytoplasm moves during expansion into the future oogonium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281520
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  • 2
    Electronic Resource
    Electronic Resource
    Gametogenesis in the green algaOedogonium cardiacum (1974)
    Springer
    Protoplasma 81 (1974), S. 297-311 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Spermiogenesis in the macandrous, filamentous green algaOedogonium cardiacum is described at the ultrastructural level. The formation of the flagellar apparatus is similar to that in zoosporogenesis. Centrioles, appearingde novo in extranuclear, electron dense material, proliferate into two rows around the nucleus. Rootlet templates concurrently form between adjacent centrioles. The two rows migrate to the side of the cell and expand into a ring configuration. The centrioles (more correctly, basal bodies) extrude flagella while rootlet microtubules extend from the rootlet templates. Other components of the flagellar apparatus, including the fibrous ring and striated fibers, also form at this time. The flagellar apparatus of a mature sperm cell resembles that of a zoospore except the components are fewer in number and some are less well developed. A heterogeneous population of Golgi bodies in differentiating spermatids either contribute vesicles to the dome of the sperm cell, or else package and secrete extracellular products which are postulated to play a role in the release of sperm from the sperm packet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275817
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Acrylamide sensitization of the heat response of the cytoskeleton and cytotoxicity in attaching and well-spread synchronous chinese hamster ovary cells (1989)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 13 (1989), S. 67-82 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeletal arrays ; heat shock ; synchronous CHO cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The vimentin intermediate filament (VIMF) network is more sensitive to heat-induced disruption than either the microtubule (MT) or microfilament (MF) cytoskeletal (CSK) arrays in G1 Chinese hamster ovary (CHO) cells (Coss and Wachsberger: Radiation Research, 1987). We therefore investigated the effect of the VIMF disruptive agent, acrylamide (Eckert: European Journal of Cell Biology 37:169-174, 1985), on the heat response of synchronous CHO cells. Cells, either in the process of spreading (G1 or S phase) or in the well-spread state (S phase), were exposed to a nontoxic concentration of 5 mM acrylamide, heated, and processed for immunofluorescence microscopy 30 min or 20 hr following the heat shock. Recovery from CSK disruption was related to cell survival.CHO cells, either in the process of spreading or in the well-spread state, were sensitized to heat-induced CSK disruption and cytotoxicity by acrylamide. Recovery from CSK disruption correlated with surviving fractions of cells treated in the G1 phase but not with surviving fractions of cells treated in the S phase and was independent of the degree of cell spreading. This correlation suggests that damage to CSK structures may contribute to the death of cells treated in G1 but not necessarily to the death of cells treated in S phase.The degree of acrylamide sensitization of heat-induced CSK disruption was greater for cells exposed to acrylamide prior to spreading than for well-spread cells. Furthermore, normal spreading of cells was prevented when they were plated into medium containing acrylamide, suggesting that acrylamide interferes with the initial stages of attachment and spreading of these cells. These observations are interpreted in relation to the possible role that VIMFs, together with cortical MFs, may play in mediating cell surface focal contacts in the initial stages of cell attachment and spreading.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970130202
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  • 4
    Electronic Resource
    Electronic Resource
    Alterations in nuclear matrix ultrastructure of G1 mammalian cells following heat shock: Resinless section electron microscopy, biochemical, and immunofluorescence studies (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 155 (1993), S. 615-634 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Heat shock is known to inhibit vital nuclear functions associated with DNA and RNA metabolism. It has been proposed that the reported heat-induced excess protein accumulation in the nuclear matrix (NM) fraction may alter NM sites crucial for DNA and RNA processing. To test this hypothesis, we examined the fine structure of the NM in synchronous populations of G1 Chinese hamster ovary cells before and after heating by using the technique of resinless section electron microscopy. Heat did induce morphological alterations in the NM. The NM of control cells contained a honeycomb-like arrangement of fibers after chromatin removal. Following heat shock, NMs appeared as more highly anastomosing networks of polymorphic fibers and an overall increase in electron density was observed. Residual nucleoli from heated NMs underwent alterations in distributions of electron density both internally and at their peripheries. The increase in electron density observed in heated NMs was accompanied by an increase in protein mass and a relatively smaller increase in RNA mass as indicated by parallel sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) and isotopic labeling (protein/DNA and RNA) studies. Some excess protein accumulation could also be directly localized onto NM fibers by use of antibodies to heterogeneous ribonucleoprotein complex antigens. It is concluded that alterations of NM fine structure can reflect the heat-stressed state of the cell, may account for the heat-induced inhibition of nucleic acid metabolism, and may be useful as an indicator of physiological or pathological stress in general. © 1993 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041550319
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  • 5
    Electronic Resource
    Electronic Resource
    Recovery of nuclear matrix ultrastructure of interphase CHO cells after heat shock (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 160 (1994), S. 97-106 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Heat shock induces changes in G1 CHO cell nuclear matrix (NM) ultrastructure that may be related to heat-induced nuclear protein accumulation (Wachsberger and Coss, 1993, J. Cell. Physiol., 155:615-634). The present study quantitates recovery of alterations in NM fine structure in CHO cells heated in G1 and compares structural recovery with recovery of bulk RNA synthesis and surviving fraction (SF). Morphology of NM preparations was quantified 30 min and 20 hr following heat shock by 1) measurement of the number of fiber anastomosing points per unit area per NM, and 2) measurement of the length of fibers between points of anastomoses within individual NMs. Architectural recovery was nearly complete within 20 hr in cells heated at 43°C or 45°C with SFs of 0.27 or greater. No recovery of architecture was observed in heated cells with SFs of approximately 0.01 or less. The residual damage to NMs was associated with RNA-containing fiber networks as determined by means of RNase gold labeling. Recovery from inhibition of RNA synthesis following heat shock was related to recovery of NM architecture. It is suggested that 1) repair of NM architecture does not require full recovery of bulk RNA synthesis, and 2) partial or complete irreversible collapse of the NM may be responsible, in part, for heat-induced, interphase cell death. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041600112
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